Cancer of the uterine cervix contributes significantly to the total cancer morbidity and mortality among women in the United States. Cytologic screening using the Papanicolaou smear has become a widely accepted modality for detecting cervical neoplastic disease. The cost-effectiveness of Papanicolaou smear screening on an annual basis has been questioned. Recently, recommendations have been made for modifying current practices by increasing the interval between successive cytologic examinations among those women identified as being at "low risk" of incidence. In no instance have the sequelae of such proposed changes been examined in terms of expected changes in incidence, survival and mortality for cancer of the cervix. The natural history of cervical neoplastic disease has been described by us and other investigators. Several cytologically defined lesions are thought to be precursors of invasive cancer of the cervix and there is wide acceptance that carcinoma-in-situ is antecedent to invasive disease. This lesion is potentially 100% curable and will, if untreated, progress to invasive cancer in the majority of cases. The transition times and probabilities of the stages of cervical neoplastic disease have been presented previously. Using these data together with age-specific incidence rates currently available from a variety of sources and available estimates of incidence, the studies proposed here will generate estimates of the incidence, survival and mortality for cervix cancer among defined populations exposed to specified cytologic screening regimens.